Control of connectivity for a voice-capable UE that will be served by a node that does not support voice-over-packet service

ABSTRACT

A mechanism to help control connectivity of a user equipment device (UE). When the UE is served by a master node (MN) that does not support VOP service, the MN will cause the UE to not have a secondary connection with a secondary node (SN) that would engage in control-plane signaling with the UE via the UE&#39;s master connection with the MN. For instance, in that situation, the MN could avoid setting up the secondary connection for the UE in the first place. Or if the secondary connection exists already, the MN could tear down that secondary connection. By causing the secondary connection to not exist, the mechanism may help to avoid problems with operation of the secondary connection as a result of the UE tuning away to facilitate voice service.

BACKGROUND

A cellular wireless network typically includes a number of basestations, that are configured to provide wireless coverage areas, suchas cells and cell sectors, in which user equipment devices (UEs) such ascell phones, tablet computers, machine-type-communication devices,tracking devices, embedded wireless modules, and/or other wirelesslyequipped communication devices (whether or not user operated), canoperate. Each base station could be coupled with a core network thatprovides connectivity with various application servers and/or transportnetworks, such as the public switched telephone network (PSTN) and/orthe Internet for instance. With this arrangement, a UE within coverageof the cellular network could engage in air interface communication witha base station and could thereby communicate via the base station withvarious application servers and other entities.

Such a network could operate in accordance with a particular airinterface protocol (or radio access technology), with communicationsfrom the base stations to UEs defining a downlink or forward link andcommunications from the UEs to the base stations defining an uplink orreverse link.

In accordance with the air interface protocol, each coverage area couldoperate on one or more carriers, each of which could be frequencydivision duplex (FDD), defining separate frequency channels for downlinkand uplink communication, or time division duplex (TDD), with a singlefrequency channel multiplexed over time between downlink and uplink use.Further, on the downlink and uplink, each such carrier could bestructured to define various physical channels for carrying informationbetween the base stations and UEs.

Over the years, the industry has embraced various “generations” of airinterface protocols, in a continuous effort to increase available datarate and quality of service for end users. These generations have rangedfrom “1G,” which used simple analog frequency modulation to facilitatebasic voice-call service, to “2G” or “3G,” such as Code DivisionMultiple Access (CDMA), which used spread spectrum coding to facilitatecircuit-switched voice service, to “4G”—such as Long Term Evolution(LTE), which facilitates mobile broadband service using technologiessuch as orthogonal frequency division multiplexing (OFDM) and multipleinput multiple output (MIMO). And most recently, the industry is nowexploring developments in “5G” and particularly “5G NR” (5G New Radio),which may use a scalable OFDM air interface, advanced channel coding,massive MIMO, beamforming, and/or other features, to support higher datarates and countless applications, such as mission-critical services,enhanced mobile broadband, and massive Internet of Things (IoT).

As the industry advances from one generation of wireless air interfacetechnology to the next, issues arise with the need for UEs to supportpotentially multiple air interface protocols at once. With thetransition from 4G to 5G, for instance, it is expected that UEs will beconfigured to support use of both technologies concurrently, with anarrangement referred to as EUTRA-NR Dual Connectivity (EN-DC). With suchan arrangement, a UE might include a 4G radio and a 5G radio, with the4G radio being served by a 4G base station concurrently with the 5Gradio being served by a 5G base station. This arrangement could helpsupport transition from 4G technology to 5G technology and may provideother benefits as well. More generally, dual connectivity couldencompass service on two or more air interface protocols concurrently,to facilitate technology transitions or for other purposes.

OVERVIEW

In a representative dual-connectivity arrangement, one base stationcould operate as a master node (MN) with which the UE initiallyconnects, and another base station could operate as a secondary node(SN) that operates to provide additional frequency bandwidth so as tosupport higher throughput or the like. For example, with an exampleimplementation of EN-DC, a 4G base station (e.g., an evolved Node-B(eNB)) could operate as the MN, and a 5GNR base station (e.g., a gigabitNode-B (gNB)) could operate as the SN.

When the UE enters into coverage of the MN, the UE could discover the MNcoverage and could responsively engage in signaling with the MN toestablish a connection between the UE and the MN, referred to as amaster connection. Further, the UE could engage in attach signaling witha core network controller via the master connection, to attach orregister for service with the network, and the core network controllercould responsively coordinate establishment for the UE of one or morebearers anchored at the MN, for carrying user-plane packet datacommunications to and from the UE.

The MN could then serve the UE with wireless packet-data communications.For instance, when packet-data arrives at the MN for transmission to theUE, the MN could allocate downlink air interface resources (e.g.,time-frequency resources) on which to transmit the data to the UE, theMN could transmit to the UE a scheduling directive that indicates thetransmission will occur on the allocated resources, and the MN couldtransmit the data to the UE as indicated. And when the UE has data totransmit, the UE could send to the MN a scheduling request, the MN couldresponsively allocate uplink resources on which the UE will transmit thedata to the MN and could transmit to the UE an associated schedulingdirective, and the UE could transmit the data to the MN accordingly.Further, other signaling communication such as acknowledgement signalingand the like could pass between the UE and the MN to help manage thesetransmissions over the master connection.

In addition, the MN could engage in a process to add a secondaryconnection for the UE, to help increase frequency bandwidth andthroughput available for the UE. For instance, the MN could direct theUE to scan for secondary coverage and could responsively receive areport from the UE that the UE detected threshold strong coverage of anSN. The MN could then responsively engage in signaling with the SN andwith the UE to coordinate establishment of a secondary connectionbetween the UE and the SN, and the MN could further engage in to preparethe SN to serve the UE, and the MN could engage in signaling with thecore network controller to cause the core network controller to splitone or more of the UE's established bearer(s) so as to have each suchbearer connect both with the MN and with the SN.

With such dual-connectivity established, the MN could serve the UE withuser-plane data communications over the master connection while the SNserves the UE with user-plane data communications over the secondaryconnection.

When the core network has data for transmission to the UE, the corenetwork could send some of that data over one leg of the UE's splitbearer to the MN for transmission over the master connection to the UE,and the core network could send other of that data over another leg ofthe UE's split bearer to the SN for transmission over the secondaryconnection to the UE. And likewise, when the UE has data to transmit,the UE could transmit some of that data over the master connection tothe MN for forwarding by the MN over a leg of the UE's split bearer, andthe UE could transmit other of the data over the secondary connection tothe SN for forwarding by the SN over another leg of the UE's splitbearer. Note that, in an alternative embodiment, the bearer split couldoccur at the MN itself, with some of the UE's data flowing between theMN and the SN.

In an example of such an arrangement, control-plane signaling related toboth the UE's communication on the master connection and the UE'scommunication over the secondary connection could flow over the masterconnection.

In particular, the MN could operate as discussed above, engaging inuser-plane communication with the UE over the master connection, andengaging in control-plane signaling with the UE over the masterconnection to schedule and otherwise manage that user-planecommunication. Further, the SN could engage in user-plane communicationwith the UE over the secondary connection, but the SN's control-planesignaling with the UE could pass through the MN and the masterconnection.

With this arrangement, when the SN has control-plane signaling (such asscheduling directives, acknowledgements of uplink user-planecommunication, etc.) to send to the UE, the SN could transmit thatcontrol-plane signaling over an inter-base-station interface to the MNand the MN could transmit the control-plane signaling over the masterconnection to the UE. Likewise, when the UE has control-plane signaling(such as scheduling requests, acknowledgements of downlink user-planecommunications, etc.) to send to the SN, the UE could transmit thatcontrol-plane signaling to the MN, and the MN could forward thecontrol-plane signaling via an inter-base-station interface to the SNfor processing.

One technical problem that can arise in this scenario is that, if the UEloses its master connection with the MN, control-plane signaling betweenthe UE and the SN could fail, and associated user-plane communicationbetween the UE and the SN could fail.

For example, if the SN provides a scheduling directive for downlinkpacket-data transmission to the UE and engages in that scheduleddownlink transmission, if that scheduling directive does not make it tothe UE due to the UE not being in master-connection communication withthe MN, then that downlink packet-data transmission may fail. Likewise,if the SN provides a scheduling directive for uplink packet-datacommunication from the UE and expects to receive that uplinktransmission from the UE, if that scheduling directive does not make itto the UE due to the UE not being in master-connection communicationwith the MN, then that uplink packet-data communication may fail.Similar problems could arise as a result of failure of othercontrol-plane communication related to the secondary connection, such asfailure of acknowledgement signaling or the like.

Without limitation, an example situation where this problem can arise isif the UE, when served by the MN, periodically tunes away from itsmaster connection with the MN. If the UE is so set to tune-awayperiodically, the MN may be aware of that tune-away schedule and mayavoid engaging in communication with the UE during times when the UE isscheduled to be tuned away. But the SN may not be aware of the UE'stuneaway schedule. And if the SN attempts to engage in control-planesignaling with the UE during times when the UE is tuned away from the MNand the master connection, that SN control-plane signaling, and perhapsassociated SN user-plane communication, could fail as discussedabove—due to the lack of a master connection over which to convey thatSN control-plane signaling to the UE.

A UE could be set to periodically tune away from its serving MN if theUE supports voice-call service and the UE is operating in a mode wherethe UE is set to be served with voice-call service by a separatenetwork, such as to be served with voice-over-circuit (VOC) service by alegacy CDMA network for instance. In that situation, while the UE isserved by the MN, the UE might also be registered for service by theseparate network and might tune away periodically from the MN to checkfor voice-call page messages or the like from the separate network.Without limitation, an example of such a mode is Single-Radio-LTE(SRLTE), where the UE has a single radio that the UE uses for either LTEcommunication with the MN or CDMA communication with a CDMA base stationbut not both concurrently.

A UE may be set to operate in such a mode in a situation where the MNitself does not support voice over packet (VOP) service, perhaps due tolack of programming or hardware to support voice coding and associatedfeatures. Some MNs in the network might support VOP service but othersmight not. If the UE ends up being served by an MN that supports VOPservice, then the UE might be set to engage in any voice calling usingVOP service served by the MN. But if the UE ends up being served by anMN that does not support VOP service, then the UE may need to operate inthe mode discussed above in order to be able to place and receive voicecalls, in which case the above-discussed problems may arise.

Disclosed herein is a mechanism to help address this problem.

In accordance with the disclosure, when a UE is served by an MN thatdoes not support VOP service, the MN will cause the UE to not have asecondary connection with an SN that would engage in control-planesignaling with the UE via the UE's master connection with the MN. Forinstance, in that situation, the MN could avoid setting up the secondaryconnection for the UE in the first place. Or if the secondary connectionexists already, the MN could tear down that secondary connection.

By causing the secondary connection to not exist in a situation wherethe UE's serving MN does not support VOP service, this process helps toavoid failure of the SN control-plane signaling at times when the UEperiodically tunes away from the MN to facilitate circuit-switchedvoice-call service or the like.

These as well as other aspects, advantages, and alternatives will becomeapparent to those reading the following description, with referencewhere appropriate to the accompanying drawings. Further, it should beunderstood that the discussion in this overview and elsewhere in thisdocument is provided by way of example only and that numerous variationsare possible.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified block diagram of an example network arrangementin which aspects of the present disclosure can be implemented.

FIG. 2 is a flow chart depicting an example method in accordance withthe disclosure.

FIG. 3 is another flow chart depicting an example method in accordancewith the disclosure.

FIG. 4 is a simplified block diagram of an example MN operable inaccordance with the disclosure.

FIG. 5 is a simplified block diagram of an example UE operable inaccordance with the disclosure.

DETAILED DESCRIPTION

An example implementation will now be described in the context of asystem including an EN-DC network and a legacy CDMA network. However, itshould be understood that the principles disclosed herein could extendto apply with respect to other scenarios as well, such as with respectto other air interface protocols and services. Further, it should beunderstood that other variations from the specific arrangements andprocesses described are possible. For instance, various describedentities, connections, functions, and other elements could be added,omitted, distributed, re-located, re-ordered, combined, or changed inother ways.

FIG. 1 is a simplified block diagram of an example network arrangement,showing at its top portion an EN-DC network 12 for providingwireless-packet-data service according to 4G LTE and 5G NR protocols,and showing at its bottom portion a legacy CDMA network 14 for providingwireless circuit-data services such as legacy circuit-switched voicecall service for instance.

EN-DC network 12 includes a representative MN 16, likely an LTE eNB, anda representative SN 18, likely a 5G NR gNB. The MN 16 and SN 18 could beco-located at a common cell site, sharing an antenna tower or otherantenna structure, and sharing baseband hardware or the like, but beingseparately defined to provide discrete 4G and 5G connections andservice. The MN and SN could each be configured to provide respectivecoverage 20, 22 on one or more carriers as discussed above, definingrespective frequency bandwidth and air interface resources for carryingcommunications wirelessly to/from served UEs.

In a representative implementation, respective coverage on each carrierof the 4G and 5G coverage 20, 22 could be divided over time into frames,subframes, timeslots, and symbol segments, and could be divided overfrequency bandwidth into subcarriers. As a result, the respectivecoverage could define an array of time-frequency resource elements, inwhich subcarriers can be modulated to carry data communications.

In each subframe, these resource elements could be divided into groupsdefining physical resource blocks (PRBs) that are allocable by theassociated base station (MN or SN) on an as-needed basis to carry datacommunications. And certain resource elements per subframe could bereserved for other purposes. In LTE for instance, a first time portionof each downlink subframe is reserved as a control region to carrydownlink control-plane signaling such as scheduling directives andacknowledgement messaging, and the low-end and high-end portions of thecarrier bandwidth in each uplink subframe are reserved as a controlregion to carry uplink control-plane signaling such as schedulingrequests. In addition, designated resource elements could be reserved tocarry other signals, such as synchronization signals, broadcast-channelsignals, reference signals, random-access signals, and the like.

As further shown, the MN and SN are each connected with a core network24, which includes a gateway system 26 and a control node 28. In anexample EPC network, the gateway system includes a serving gateway (SGW)and a packet-data network gateway (PGW), with the SGW having acommunication interface 30 with the MN and a communication interface 32with the SN, and with the PGW providing connectivity with a transportnetwork 34 such as the Internet or a private network. And the controlnode 26 could be a mobility management entity (MME), which could have acommunication interface 36 with the MN and a communication interface 38with the gateway system 28 (e.g., with the SGW).

Also shown accessible on or via transport network 34 is an InternetMultimedia Subsystem (IMS) 40. The IMS supports VOP service (and equallyother type of packet-based real-time media services) for served UEs. Forinstance, the IMS may support Session Initiation Protocol (SIP)signaling with served UEs to set up and manage VOP calls, and the IMSmay include a media server to bridge and connect such calls to remotecall parties or the like. Thus, a served UE might engage in SIPsignaling with the IMS to set up an incoming or outgoing VOP call,establishing a packet-based real-time media session (e.g., Real-timeTransport Protocol (RTP) session) between the UE and IMS, which the IMScould bridge with a remote party, to facilitate voice call communicationbetween the UE and the remote party.

When a UE 42 initially enters into coverage of this EN-DC network 12,the UE could discover coverage of the MN, such as by scanning predefined4G carriers to find a synchronization signal from the MN and thenevaluating to determine that a reference signal from the MN is strongenough to justify connecting. The UE could then engage in random-accesssignaling and RRC signaling as discussed above to establish an RRCconnection with the MN, defining a master connection between the UE andthe MN.

The UE could then engage in attach signaling with the control node 26,via that master connection and MN, to register for service with thenetwork 12. And after authenticating the UE, the control node 26 couldresponsively coordinate setup for the UE of at least one user-planebearer including an S1-U portion extending over interface 30 between theMN and the gateway system. Further, the control node 26 and/or the UEcould provide the MN with a set of capabilities data describingcapabilities of the UE, and the MN could store that data in a contextrecord associated with the UE's master connection.

In a basic arrangement, the control node 26 could set up a best-effortsbearer for the UE at this stage, to enable the UE to engage in generalInternet data communication. Further, if the UE supports VOP service andif the MN supports VOP service, the control node 26 could also set upfor the UE an IMS signaling bearer that the UE could use to engage inSIP signaling with the IMS 40 as discussed above.

As noted above, the MN could further work to set up for the UE asecondary connection served by SN 18, with the MN functioning as ananchor point for control-plane signaling related to both the MN's masterconnection with the UE and the SN's secondary connection with the UE. Inparticular, the MN could send to the UE an RRC message that directs theUE to scan for and report any threshold coverage that the UE detects on5G carriers. And upon receipt of such a report from the UE specifyingthat the UE detected threshold strong coverage of coverage of SN 18, theMN could then engage in signaling to set up the secondary connection.For instance, the MN could engage in inter-base-station signaling withthe SN to prepare the SN to serve the UE over the secondary connection,(ii) the MN could send a directive to the UE to cause the UE to engagein signaling with the SN to establish the secondary connection, and(iii) the MN could engage in signaling with the control node 26 to causethe control node to coordinate setup for the UE of a split bearerincluding the existing leg with MN over interface 30 and a new leg withSN over interface 32.

As discussed above, the MN and SN could then cooperatively provide theUE with EN-DC service.

For example, as the gateway system receives downlink data destined tothe UE, the gateway system could send some of that data respectivelyover each leg of the UE's split bearer. And the MN and SN could eachschedule transmission to the UE of their respective portion of thatdata.

In this process, for communication of the data from the MN to the UE,the MN would generate and transmit over its master connection to the UEone or more scheduling directives that designate which PRBs will carrydata to the UE over the master connection from the MN, and the MN wouldtransmit the data to the UE in the designated PRBs of the masterconnection. Further, the MN would receive associated UE acknowledgementsignaling from the UE over the master connection as well.

Likewise, for communication of the data from the SN to the UE, the SNwould generate scheduling directives that would designate which PRBswill carry data to the UE over the secondary connection from the SN, andthe SN would transmit the data to the UE in the designated PRBs of thesecondary connection. However, the SN would transmit its schedulingdirectives over an inter-base-station interface to the MN for the MN totransmit over the master connection to the UE. And associatedacknowledgement signaling from the UE to the SN would likewise pass overthe master connection to the MN and over the inter-base-stationinterface from the MN to the SN.

In such a system where the UE will engage in VOP service, the MN mightbe configured to support the VOP service, but the SN might not. Thus,while the UE may make use of its EN-DC connections to engage inhigh-data-rate packet-data communications generally, the UE may use justits master connection with the MN, and not its secondary connection withthe SN, to engage in VOP service. To facilitate voice service once theUE has connected with the MN, the UE may engage in SIP signaling withthe IMS via the US's master connection and the UE's IMS signaling bearerto register with the IMS, so that the IMS will know where to reach theUE for calls placed to the UE. And when the UE has a voice call to placeor the IMS has a voice call to connect to the UE, the UE might engage inSIP signaling with the IMS via the UE's master connection and the UE'sIMS signaling bearer, and the UE may then engage in the resulting VOPcall through the same path.

Turning next to the lower portion of FIG. 1, the example CDMA network isshown including a representative CDMA base station (base transceiverstation (BTS)) 44. This BTS could be co-located with the MN and SN at acommon cell site, sharing an antenna tower or other antenna structure,and sharing other equipment. But the BTS provides its own respectiveCDMA coverage 46. The CDMA coverage could be provided on a carrier, suchas a 1.25 MHz carrier, with various dedicated circuits or channelsdefined on the carrier through spread-spectrum modulation usingrespective Walsh codes and a pseudo-random noise offset. For instance,the carrier might define a plurality of discrete traffic channels,access channels, paging channels, and the like.

As further shown, the BTS coupled with a core network 48. Core network48 may include various nodes (not shown) such as a base stationcontroller (BSC), a mobile switching center (MSC), a home locationregister (HLR), an interworking function (IWF), and a packet-dataserving node (PDSN), among other possibilities. Further, the corenetwork could include or be interconnected with a soft-switch 50,possibly instead of the MSC, which could interface betweencircuit-switched voice communications and associated signaling in theCDMA network and VOP communications and signaling at the IMS.

When a UE enters into coverage of the CDMA network, the UE couldregister for service with the CDMA network by transmitting aregistration message over an access channel to the BTS, which the BTScould forward to the MSC. And the MSC could engage inregistration-notification signaling with the HLR to record the fact thatthe UE is being served by the BTS.

When the UE seeks to place a voice call, the UE could then transmit anorigination request message over an access channel to the BTS, which theBTS could forward to the MSC, and the MSC and/or soft-switch couldengage in signaling to set up the call via the IMS. Further, the BTScould assign a dedicated traffic channel to the UE, to enable the UE toproceed with the call.

And when the core network 46 receives signaling indicating an incomingvoice call for the UE, the network could route the call to the BTS, andthe BTS could page the UE during an instance of a periodic paginginterval in which the UE is scheduled to scan the CDMA air interface forpage messages. Upon receipt of that page message, the UE could thentransmit an page response on an access channel to the BTS, the BTS couldassign a dedicated traffic channel to the UE, and the call can proceed.

In a representative implementation, the UE could be programmed to preferoperation with 4G over operation with CDMA network, so as to benefitfrom high-data-rate packet-data service. Thus, when the UE is initiallyscanning for coverage and service, if the UE finds both coverage of the4G MN and coverage of the CDMA BTS, the UE may decide to establish a 4Gconnection with the MN as discussed above rather than registering forCDMA service.

On the other hand, the UE may need to be able to support voice callservice—such as to facilitate emergency calling or for other reasons.Therefore, at issue for the UE may be whether the MN supports VOPservice. To enable the UE to determine this, the MN could broadcast asystem message that includes a Boolean “VOPS” value of either 1 toindicate that the MN support VOP service or 0 to indicate that the MNdoes not support VOP service. And the UE could read that broadcastmessage to determine whether the MN supports VOP service. Alternatively,the UE could determine in another manner whether the MN supports VOPservice.

If the UE thereby determines that the MN supports VOP service, then theUE could connect with the MN and could then register with the IMS and beset to engage in IMS-based VOP service via the MN. Whereas, if the UEthereby determines that the MN does not support VOP service, then the UEcould instead enter into SRLTE mode.

In particular, the UE could temporarily tune away from its masterconnection with the MN and engage in signaling with BTS 42 to registerfor CDMA service as discussed above, and the UE could then tune back toits existing connection with the MN. As the UE is served by the MN, theUE could then periodically tune away from the MN to check for CDMA pagemessages directed to the UE. The UE could have a particular paging slotcycle in the CDMA system, and the UE could tune away from the MN to theBTS periodically per that slot cycle. The UE could also inform the MNthat the UE is operating in SRLTE mode, such as by sending to the MN atracking area update or other signaling message carrying an indicationthat the UE is operating in SRLTE mode and perhaps an indication of theUE's slot cycle if the MN does not have that information already. Thatway, while the UE is served by the MN but is operating in SRLTE mode,the MN could avoid transmitting any communications during times when theUE is scheduled to be tuned away from the MN.

As discussed above, if the UE has dual connectivity with the MN and theSN, the UE's tuning away from the MN to check for CDNA page messagescould have a detrimental impact on the UE's secondary connection withthe SN. Namely, as noted above, the SN may be unaware of the fact the UEis tuned away from time to time, and the SN may provide control-planesignaling to the UE during those times. When the SN sends that signalingto the MN for transmission to the UE, the MN may then be unable toprovide the transmission when desired. And as a result, thecontrol-plane signaling (and perhaps associated user-plane signaling)from the SN to the UE may fail.

Per the present disclosure as discussed above, an approach to help solvethis problem is to have the MN cause the UE's secondary connection withthe SN to not exist, in response to determining that the UE will beoperating in a mode in which the UE periodically tunes away from the MN.More particularly, the MN could avoid setting up the UE's secondaryconnection with the SN or could tear down such a connection if it existsalready, in a situation where the MN does not support VOP service. Bycausing the UE's secondary connection to not exist in that situation,the UE could operate in SRLTE mode or the like without risk of creatingproblems with the secondary connection.

If the secondary connection for the UE does not already exist, the MNcould avoid setting up that secondary connection by (i) forgoingsignaling to the UE to cause the UE to scan for coverage of the SNand/or to connect with the SN, (ii) forgoing signaling to the SN toprepare the SN to serve the UE over the secondary connection, and/or(iii) foregoing signaling to the control node 26 to cause the controlnode to set up a split bearer leg connected with the SN, among otherpossibilities.

Whereas, if the secondary connection for the UE already exists, the MNcould tear down that secondary connection by carrying out operationssuch as (i) signaling to the UE to cause the UE to discontinue use ofthe secondary connection, (ii) signaling to the SN to cause the SN todiscontinue the secondary connection with the UE, and (iii) signaling tothe control node 26 to cause the control node to tear down a splitbearer leg that was connected with the SN for the UE.

By way of example, this process could address a situation where a UE isserved with dual-connectivity by the MN and SN, where the SN engages incontrol-plane signaling with the UE via the UE's master connection withthe MN, and where the MN does not support VOP service. In thatsituation, at the initiation of the MN or the UE, the MN could tear downthe UE's secondary connection, so that the UE could then periodicallytune away for voice service without having control-plane signalingissues with the SN.

Alternatively, the process could address a situation where the UE isserved by just the MN (without dual-connectivity, where the MN mightconsider adding for the UE a secondary connection with an SN with whichthe UE would engage in control-plane signaling via the UE's masterconnection with the MN, and where the MN does not support VOP service.In that situation, at the initiation of the MN or UE, the MN could avoidsetting up the secondary connection for the UE, so as to avoid creatinga situation where the UE's periodically tuning away for voice servicewould create problems with the secondary connection.

As a more specific example of this, consider a scenario where the UE wasserved by a different MN than that shown in FIG. 1, where that MNsupported VOP service, and where the UE handed over from being served bythat MN to being served by MN 16 shown in FIG. 1 that does not supportVOP service. In that handover process, the MN 16 might normally add forthe UE a secondary connection with SN 18 or may make use of an existingsecondary connection that was in place for the UE.

In that scenario, during and/or after setup of the master and secondaryconnections for the UE with MN 16 and SN 18 respectively, the UE couldread a broadcast message from MN 18 and determine that the MN 16 doesnot support VOPS. And in response, the UE could then transition tooperate in SRLTE mode and transmit to MN a tracking area update messageor other message that carries one or more parameter values (i) that willindicate to the MN that the UE will now operate in SRLTE mode, so thatthe MN can handle communication scheduling for the UE accordingly, and(ii) to which the MN will respond by tearing down the UE's secondaryconnection with SN 18. Although tracking area update messages maynormally be used to inform a serving base station that a UE has enteredinto a new tracking area, this process could thus make use of a trackingarea update message as a way to cause its serving base station (MN) totear down the UE's connection with another base station (SN).

Alternatively, MN 16 could discover during or after the handover of theUE to MN 16 that the UE is voice capable (e.g., per UE capabilitiesdata) and that the source MN from which the UE handed over supported VOPservice (e.g., per neighbor MN data). Given that MN 16 does not supportVOP service, MN 16 could then responsively tear down a secondaryconnection that has been established for the UE or could responsivelyavoid setting up such a secondary connection for the UE.

FIG. 2 is a flow chart depicting an associated method. This method couldbe carried out by an MN and/or by the UE, to help control connectivityof the UE.

As shown in FIG. 2, at block 52, the method involves detecting (i) thatthe UE will be served with wireless packet-data service by the MN over amaster connection between the UE and the MN and (ii) that the MN doesnot support VOP service of the UE. And at block 54, the method involves,responsive to at least the detecting, while (i.e., although) the UE willbe served by the MN over the master connection, causing the UE to not beserved, concurrently with the UE being served by the MN over the masterconnection, with wireless packet-data service by an SN that would engagein user-plane signaling with the UE over a secondary connection betweenthe UE and the SN and that would engage in control-plane signaling withthe UE over the master connection.

In line with the discussion above, the act of causing the UE to not beserved with wireless packet-data service by the SN that would engage incontrol-plane signaling with the UE over the master connection couldthus help to avoid failure of the control-plane signaling resulting fromthe UE periodically tuning away from the MN to facilitate VOC service.For instance, this could apply where the MN is an eNB, the SN is a gNB,and the UE tuning away from the MN to facilitate VOC service involvesthe UE tuning away from the eNB to check for pages from a base stationoperating in accordance with CDMA.

As further discussed above, the detecting operation could be carried outwhile the UE is already served by the MN over the master connection andcould involve detecting that the UE will continue to be served by the MNover the master connection. Further, the act of causing the UE to not beserved with wireless packet-data service by the SN that would engage incontrol-plane signaling with the UE over the master connection couldinvolve the MN forgoing setup of the secondary connection for the UE.

Further, the detecting operation could be carried out while the UE isalready served with wireless packet-data service by the SN, and the actof causing the UE to not be served with wireless packet-data service bythe SN could involve the MN working to tear down the secondaryconnection between the UE and the SN.

In addition, as discussed above, the detecting operation could becarried out by the UE, and act of causing the UE to not be served withwireless packet-data service by the SN could involve the UE signaling tothe MN to cause the MN (i) to forgo setup of the secondary connectionfor the UE or (ii) to tear down the secondary connection if thesecondary connection is already set up. For instance, the UE couldtransmit to the MN over the master connection a tracking-area-updatemessage that informs the MN that the UE is going to operate in a mode inwhich the UE will periodically tune away from the MN to facilitate VOCservice, even though the UE has not entered into a new tracking area.

Alternatively, the detecting operation could be carried out by the MN,and the act of causing the UE to not be served with wireless packet-dataservice by the SN could involve the MN (i) forgoing setup of thesecondary connection for the UE or (ii) tearing down the secondaryconnection if the secondary connection is already set up.

Still further, as discussed above, the MN could be a target MN forhandover of the UE from a source MN to the target MN, and the method becarried out in relation to that handover, in a scenario where the sourceMN supports VOP service, so that the UE would be transitioning from asituation where its serving MN supports VOP service to a situation whereits serving MN does not support VOP service. And in that case, the actof causing the UE to not be served with wireless packet-data service bythe SN could likewise involve the MN (i) forgoing setup of the secondaryconnection for the UE or (ii) tearing down the secondary connection ifthe secondary connection is already set up.

FIG. 3 is another flow chart depicting an associated method, to controlconnectivity of a UE.

As shown in FIG. 3, at block 56, the method includes detecting handoverof the UE from a source master MN that supports VOP service of the UE toa target MN that does not support VOP service of the UE. And at block58, the method includes, responsive to at least the detecting, causingthe target MN to provide the UE with single-connectivitywireless-packet-data service over a master connection between the UE andthe MN rather providing the UE with dual-connectivitywireless-packet-data service over (i) the master connection between theUE and the MN and (ii) a secondary connection between the UE and an SNthat would engage in control-plane signaling with the UE over the masterconnection.

Various features described above can be applied in this context, andvice versa.

In line with the discussion above, for instance, the act of providingthe UE with the single-connectivity wireless-packet-data service ratherthan with the dual-connectivity wireless-packet-data service could helpto avoid failure of the control-plane signaling resulting from the UEperiodically tuning away from the MN to facilitate VOC service, againperhaps the scenario described above among other possibilities.

Further, the method could be carried out by the target MN, in which casethe act of causing the causing the target MN to provide the UE withsingle-connectivity wireless-packet-data service rather providing the UEwith dual-connectivity wireless-packet-data service could involve acontroller of the target MN causing the target MN to forgo adding thesecondary connection for the UE.

Alternatively, the method could be carried out by the UE, in which casethe act of detecting handover of the UE from the source MN that supportsVOP service of the UE to a target MN that does not support VOP serviceof the UE could include, in association with the handover, the UEreceiving from the target MN a broadcast message that indicates thetarget MN does not support VOP service.

FIG. 4 is a simplified block diagram of an example MN operable inaccordance with present disclosure. As shown, the example NB includes awireless communication interface 60, a backhaul interface 62, and acontroller 64, all of which may be communicatively linked together by asystem bus, network, or other connection mechanism 66 and/or could beintegrated together or distributed in various ways.

In this example arrangement, the wireless communication interface 60 maybe configured to provide cellular coverage and to engage in airinterface communication with served UEs. As such, wireless communicationinterface 60 may comprise an antenna structure, which may be towermounted or may take other forms, and associated components such as apower amplifier and a wireless transceiver, so as to facilitateproviding a coverage area defining an air interface having a downlinkand an uplink, and engaging in transmission and reception of bearer andcontrol data over the air interface in accordance with an air interfaceprotocol such as any of those noted above. Further, backhaul interface62 may comprise a wired or wireless interface, such as an Ethernetnetwork communication interface, configured to support communicationwith other entities, such as with various core network entities andother base stations for instance.

Controller 64 may then comprise control logic to cause the MN to carryout particular operations including those described herein. As such, thecontroller 64 may take various forms, including but not limited to aprocessing unit including one or more processors (e.g., general purposemicroprocessors and/or dedicated processing units) and non-transitorydata storage (e.g., one or more volatile and/or non-volatile storagecomponents, such as magnetic, optical, or flash storage) holding programinstructions executable by the processing unit to cause the MN to carryout various operations described herein. It should also be understoodthat the present disclosure also contemplates a non-transitory computerreadable medium having encoded thereon program instructions executableto carry out such operations as well.

In an example implementation, for instance, the operations of the MNcould include detecting (i) that a UE will be served with wirelesspacket-data service by the MN over a master connection between the UEand MN, (ii) that the UE is voice-capable, and (ii) that the MN does notsupport VOP service of the UE. And the operations could further include,responsive to at least the detecting, causing the UE to not be served,concurrently with the UE being served by the MN over the masterconnection, with wireless packet-data service by an SN that would engagein user-plane signaling with the UE over a secondary connection betweenthe UE and the SN and that would engage in control-plane signaling withthe UE over the master connection.

And as discussed above, the act of causing the UE to not be served withwireless packet-data service by the SN that would engage incontrol-plane signaling with the UE over the master connection couldhelp to avoid failure of the control-plane signaling resulting from theUE periodically tuning away from the MN to facilitate VOC service, inthe scenario described above or in other scenarios.

FIG. 5 is a simplified block diagram of an example UE operable inaccordance with the present disclosure. A shown, the example UE includesa user interface 68, a wireless communication interface 70, and acontroller 72, all of which may be communicatively linked together by asystem bus, network, or other connection mechanism 74 and/or could beintegrated together or distributed in various ways.

In this example arrangement, the user interface 68 (which might beomitted if the UE is not user operated, such as if the UE is anautomated voice communication device of some sort) could include inputand output components that facilitate user interaction with the UE. Thewireless communication interface 70 could then be configured to beserved by base stations as discussed above, in accordance with agreedair interface protocols, and could comprise an antenna structure, poweramplifier, and wireless transceiver.

And the controller 72 could comprise control logic to cause the UE tocarry out particular operations including those described herein. Forinstance, the controller 72 could include a processing unit includingone or more processors (e.g., general purpose microprocessors and/ordedicated processing units) and non-transitory data storage (e.g., oneor more volatile and/or non-volatile storage components, such asmagnetic, optical, or flash storage) holding program instructionsexecutable by the processing unit to cause the UE to carry out variousoperations described herein. And here too, the present disclosure alsocontemplates a non-transitory computer readable medium having encodedthereon program instructions executable to carry out such operations aswell.

Exemplary embodiments have been described above. Those skilled in theart will understand, however, that changes and modifications may be madeto these embodiments without departing from the true scope and spirit ofthe invention.

We claim:
 1. A method for controlling connectivity of a user equipmentdevice (UE), the method comprising: detecting (i) that the UE will beserved with wireless packet-data service by a master node (MN) over amaster connection between the UE and MN and (ii) that the MN does notsupport voice-over-packet (VOP) service of the UE; and responsive to atleast the detecting, while the UE will be served by the MN over themaster connection, causing the UE to not be served concurrently by asecondary node (SN) that would engage in user-plane signaling with theUE over a secondary connection between the UE and the SN and that wouldengage in control-plane signaling with the UE over the masterconnection, wherein causing the UE to not be served concurrently by theSN while the UE will be served by the MN over the master connectioncomprises causing the UE to operate with single connectivity with the MNrather than with dual connectivity with the MN and the SN, and whereincausing the UE to not be served concurrently by the SN that would engagein control-plane signaling with the UE over the master connection helpsto avoid failure of the control-plane signaling resulting from the UEperiodically tuning away from the MN to facilitate voice-over-circuit(VOC) service.
 2. The method of claim 1, wherein the MN is an evolvedNode-B (eNB), wherein the SN is a gigabit Node-B (gNB), and wherein theUE tuning away from the MN to facilitate VOC service comprises the UEtuning away from the eNB to check for pages from a base stationoperating in accordance with Code Division Multiple Access (CDMA). 3.The method of claim 1, wherein the detecting is carried out while the UEis already served by the MN over the master connection, and wherein thedetecting involves detecting that the UE will continue to be served bythe MN over the master connection.
 4. The method of claim 3, wherein thecausing of the UE to not be served concurrently by the SN that wouldengage in control-plane signaling with the UE over the master connectioncomprises the MN forgoing setup of the secondary connection for the UE.5. The method of claim 3, wherein the detecting is carried out while theUE already served with wireless packet-data service by the SN, andwherein the causing of the UE to not be served concurrently by the SNcomprises the MN working to tear down the secondary connection betweenthe UE and the SN.
 6. The method of claim 1, wherein the detecting iscarried out by the UE, and wherein the causing of the UE to not beserved concurrently by the SN comprises the UE signaling to the MN tocause the MN (i) to forgo setup of the secondary connection for the UEor (ii) to tear down the secondary connection if the secondaryconnection is already set up.
 7. The method of claim 6, wherein the UEsignaling to the MN comprises the UE transmitting to the MN over themaster connection a tracking-area-update message that informs the MNthat the UE is going to operate in a mode in which the UE willperiodically tune away from the MN to facilitate VOC service.
 8. Themethod of claim 7, carried out even though the UE has not entered a newtracking area.
 9. The method of claim 1, wherein the detecting iscarried out by the MN, and wherein the causing of the UE to not beserved concurrently by the SN comprises the MN (i) forgoing setup of thesecondary connection for the UE or (ii) tearing down the secondaryconnection if the secondary connection is already set up.
 10. The methodof claim 1, wherein the MN is a target MN, the method being carried outin relation to handover of the UE to the target MN from a source MN thatsupports VOP service of the UE.
 11. The method of claim 10, wherein thecausing of the UE to not be served concurrently by the SN comprises theMN (i) forgoing setup of the secondary connection for the UE or (ii)tearing down the secondary connection if the secondary connection isalready set up.
 12. A method for controlling connectivity of a userequipment device (UE), the method comprising: detecting handover of theUE from a source master node (MN) that supports voice-over-packet (VOP)service of the UE to a target MN that does not support VOP service ofthe UE; and responsive to at least the detecting, causing the target MNto provide the UE with single-connectivity wireless-packet-data serviceover a master connection between the UE and the target MN ratherproviding the UE with dual-connectivity wireless-packet-data serviceover (i) the master connection between the UE and the target MN and (ii)a secondary connection between the UE and a secondary node (SN) thatwould engage in control-plane signaling with the UE over the masterconnection, wherein providing the UE with the single-connectivitywireless-packet-data service rather than with the dual-connectivitywireless-packet-data service helps to avoid failure of the control-planesignaling resulting from the UE periodically tuning away from the targetMN to facilitate voice-over-circuit (VOC) service.
 13. The method ofclaim 12, wherein the target MN is an evolved Node-B (eNB), wherein theSN is a gigabit Node-B (gNB), and wherein the UE tuning away from thetarget MN to facilitate VOC service comprises the UE tuning away fromthe eNB to check for pages from a base station operating in accordancewith Code Division Multiple Access (CDMA).
 14. The method of claim 12,carried out by the target MN, wherein causing the target MN to providethe UE with single-connectivity wireless-packet-data service ratherproviding the UE with dual-connectivity wireless-packet-data servicecomprises a controller of the target MN causing the target MN to forgoadding the secondary connection for the UE.
 15. The method of claim 12,carried out by the UE, wherein detecting handover of the UE from thesource MN that supports VOP service of the UE to a target MN that doesnot support VOP service of the UE includes receiving by the UE from thetarget MN a broadcast message that indicates the target MN does notsupport VOP service.
 16. A master node (MN) configured to controlconnectivity of a user equipment device (UE), the MN comprising: awireless communication interface configured to engage in wirelesscommunication with the UE; a backhaul network interface through tocommunicate with other entities; and a controller configured to causethe MN to carry out operations including: (a) detecting (i) that a UEwill be served with wireless packet-data service by the MN over a masterconnection between the UE and MN, (ii) that the UE is voice-capable, and(ii) that the MN does not support voice-over-packet (VOP) service of theUE, and (b) responsive to at least the detecting, causing the UE to notbe served, concurrently with the UE being served by the MN over themaster connection, by a secondary node (SN) that would engage inuser-plane signaling with the UE over a secondary connection between theUE and the SN and that would engage in control-plane signaling with theUE over the master connection, wherein causing the UE to not be servedconcurrently with the UE being served by the MN over the masterconnection comprises causing the UE to operate with single connectivitywith the MN rather than with dual connectivity with the MN and the SN,and wherein causing the UE to operate with single connectivity with theMN rather than with dual connectivity with the MN and the SN helps toavoid failure of the control-plane signaling resulting from the UEperiodically tuning away from the MN to facilitate voice-over-circuit(VOC) service.
 17. The MN of claim 16, wherein the MN is an evolvedNode-B (eNB), wherein the SN is a gigabit Node-B (gNB), and wherein theUE tuning away from the MN to facilitate VOC service comprises the UEtuning away from the eNB to check for pages from a base stationoperating in accordance with Code Division Multiple Access (CDMA).